Field of the Invention
The invention relates to a controller for an occupant protection device in a motor vehicle. The controller has a control unit, a first interface for receiving data, and a further interface for the data interchange with a control device that is disposed remote from the controller and is operable in dependence on vehicle-specific characteristic operating values. The invention also relates to a control system with such a controller, as well as to a method of transmitting data in such a control system for an occupant protection device in a motor vehicle.
Controllers for occupant protection devices in motor vehicles usually have a control unit, a memory and various interfaces for connecting remote control devices, such as sensors or actuators for example. In that case, the controller is usually placed centrally in the vehicle, for example fastened on the vehicle tunnel. The control devices are arranged outside. If such a control device is, say, a sensor for picking up transverse accelerations, it is preferably fastened on a side part of the vehicle or a transverse member of the vehicle. A control device designed as a firing device for a driver's or passenger's airbag is preferably fastened on the steering wheel or dashboard. Furthermore, the controller described above usually has a diagnostic interface, generally for the reading in and out of diagnostic information and data during repair or maintenance cycles.
The prior art control system described in European published patent application EP 0 693 401 A2 has a controller disposed centrally in the vehicle, with acceleration sensors for longitudinal vehicle acceleration and transverse vehicle acceleration, as well as a control unit and a memory. Furthermore, a plurality of interfaces for the connection of firing devices are provided, as well as two interfaces for the connection of outside sensor devices. One sensor device is in this case arranged on each side of the vehicle for picking up transverse vehicle accelerations.
Depending on their use in a certain type of motor vehicle, both the central controller and the outside sensor devices require individual characteristic operating values/parameters provided for the respective vehicle type. Such characteristic operating values may be, for example, parameters for a triggering algorithm executed in the controller or else, according to the above-mentioned EP 0 693 401, threshold values for the sensor devices: in each sensor device, the measured transverse vehicle acceleration is classified on the basis of given threshold values. The class determined is then fed to the controller via the corresponding interface.
Until now, each controller and each control device has been provided with the associated characteristic operating values via its respectively own interface before being installed in the motor vehicle. This has generally been done by the supplier prior to shipping. Each controller or each control device has then been color-coded or mechanically coded in such a way that it was immediately evident to the assembly fitter which controller or which control device is intended for which motor vehicle type, in order that the controller or control device contains correct characteristic operating values and that it is functionally in order for protection of the occupants. The color-coding or mechanical coding requires extensive, differentiated stock keeping both at the supplier's and at the automobile manufacturer's as well as correspondingly complex logistics. The interface provided for each control device specifically for feeding in characteristic operating values requires intensive use of components and is complex to manufacture.
The international publication WO 93/20490, which is determinative of the genus herein, discloses an integrated network with controllers. Each controller contains sets of parameters for all possible motor vehicle types in which the controller can be used. After installation in the vehicle and the networking of controllers prepared in this way, the end-of-tape programmer transfers to a selected one of these controllers an indicator for the selection of a specific set of parameters for each controller. The indicator is transmitted from the selected controller via the network to the other controllers, which then form the corresponding selection of the set of parameters for the operation of the control device.
A disadvantage of the prior art control system is that each controller must have a relatively large memory area available for receiving all the conceivable vehicle-dependent characteristic data. Since these characteristic data are generally stored in a ROM, the known control system is extremely unsuitable for changes to be made, for example when further operating parameters for new motor vehicle types are added.